Conventional flush toilets are typically supplied water through a line from a manually available shutoff valve, and into a valve apparatus inside the tank. Some valve mechanisms use a float mounted at the end of a lever arm while others use a vertically sliding float, while others use static water pressure to indicate when the flush tank or reservoir is full.
Within the tank an overflow tube is provided to enable small leaks of the internal valve, or small internal valve failures to enter the toilet tank overflow tube and pass to the toilet bowl. Since the toilet bowl flow operates by passing its volume over a static pressure head dam at the rear and or base of the toilet, additional flow into the overflow tube simply continues into the bowl and over the dam at the rear and base of the toilet.
The flow path from the bowl, through the dam and into the floor pipe fitting is relatively small compared to the volume of water in each flush. This rapid flow helps to sweep the bowl, but because the flow is restricted, a significant kinetic energy of flow takes the toilet bowl to a level lower than its level would be if it were determined by the height of the dammed up water within the toilet fixture. This kinetic energy drains the bowl level lower than it would have based upon the level of the overflow damn in the fitting, because the mass of flow and its kinetic energy continues to siphon water out of the bowl for a second or so at the end of the flush. This typically occurs along with the pull of air and the gargling sound heard when the upper part of the bowl is completely drained.
If the bowl was left at this level, the volume of water for the next flush would be partially spent in refilling the bowl and would have a lesser volume available to apply to the static head within the bowl to cause a complete flush in the next cycle. In essence, the next flush would be only half of a flush, and at low velocity. This results in the need for a further flush, assuming that the bowl is left in a filled state by the half flush.
To overcome the above problems, most toilet fill valves have provided for a first flow path of water into the toilet tank for refill and a second flow path through a small plastic tube mounted to direct flow into the toilet tank overflow pipe to provide a small stream of water to allow the toilet bowl to re-fill at the same time that the toilet tank refills. During refill, the bowl will have stabilized, and a stream of water into the overflow tube will bring the bowl fully up to a level of the internal dam or trap within the toilet bowl. This will insure that upon the next flush, that the complete volume of water in the toilet tank will be applied to developing a full static head to be applied to a fully rushing velocity flush so that the bowl will be swept clean. In other words, it prevents part of the toilet tank contents from being wasted in re-filling the bowl leaving a lesser amount of water available for developing a fully rushing velocity flush. If the system for providing additional water into the overflow tube provides too much water, the excess will escape over the dam or trap at the base of the appliance.
However, the use of a side stream of water from the refill valve is not exact. The side stream will have a low flow where the local water pressure is low and a high flow where the water pressure is high. Where the flow rate is too small, the complete valve assembly can be replaced in order to provide adequate functioning. With increasing community needs for water conservation there is a need to conserve water and for toilet appliance to provide only as much water as is needed for proper operation. The user needs to be at minimum able to forego excess water introduced into the bowl which will be wasted over the overflow dam.
One such solution proposed appears in U.S. Pat. No. 6,823,889 to Schuster, incorporated by reference herein. The Schuster reference suggests a more complex and more expensive specialized toilet valve which includes an adjustable pressure overflow tube line valve in the toilet tank valve body near the point where the overflow refill tube leaves the toilet tank valve. The overflow tube line valve is located within the toilet tank refill valve so that it can handle the pressure from reduction in the flow of the overflow tube line, which can range from full open to a zero flow rate. The solution, though expensive, enables users to set the flow rate for the amount of water to be introduced into the overflow tube. The user can reduce this refill flow by adjusting the valve.
This solution works well where users have the funds to invest in a new toilet tank fill valve, as well as the high labor rates associated with plumbing services. Further, some time is required for the installer to run the valve through several flushes to determine the optimum operating setting for the complex specialized device. Further, the replaced toilet tank refill valve will typically be disposed of despite the fact that it remains in operating condition. In particular, an institutional facility replacing its valves would generate a significant volume of used toilet tank refill valves having very little market value. The loss of value from a change out and in wasted valves would make the value of the water savings minuscule by comparison. The expensive solution of the Schuster reference may work well if employed as a replacement for a defective toilet tank but is prohibitively expensive and burdensome for any water saving retrofit plan.
What is needed, however, is a solution which is not expensive, not complex, and does not require replacement of the functioning toilet tank refill valve. The needed solution should give the user practical control ability over the amount of water entering the refill tube. Further, the solution should be installable in a minimum amount of time and by ordinary people. The installation should not, unlike a toilet tank valve replacement, subject the user's facility to flooding, water shutoff, leaks about the toilet tank fittings and the like. The needed solution should be achieved without tools.